An imaging system may play a significant role in the medical filed. An imaging system may generate and/or process a medical image (e.g., a CT image, a PET image, an MRI image, etc.) for medical diagnose or radioactive therapy. For instance, a CT image of a breast may be used to screen a lump in the breast. Usually, a medical image may be adjusted, in order to facilitate a doctor to identify a potential lesion. For instance, the image may be denoised and/or enhanced by different techniques of image processing. However, the adjustment for the image may be inefficient and/or ineffective. For instance, an edge of a region of interest may be missed; gray levels in the image may be uneven; or imaging noise may be enhanced. Hence, image processing technique(s) that may enhance a contrast of the image and/or denoise the image, may be desirous for the imaging system.